Climate change will threaten fish by drying out Southwest US streams, research predicts

Aug 18, 2014 by Emily Caldwell

Fish species native to a major Arizona watershed may lose access to important segments of their habitat by 2050 as surface water flow is reduced by the effects of climate warming, new research suggests.

Most of these fish species, found in the Verde River Basin, are already threatened or endangered. Their survival relies on easy access to various resources throughout the river and its tributary streams. The species include the speckled dace (Rhinichthys osculus), roundtail chub (Gila robusta) and Sonora sucker (Catostomus insignis).

A key component of these streams is hydrologic connectivity – a steady flow of surface water throughout the system that enables fish to make use of the entire watershed as needed for eating, spawning and raising offspring.

Models that researchers produced to gauge the effects of climate change on the watershed suggest that by the mid 21st century, the network will experience a 17 percent increase in the frequency of stream drying events and a 27 percent increase in the frequency of zero-flow days.

"We have portions of the channel that are going to dry more frequently and for longer periods of time," said lead author Kristin Jaeger, assistant professor in The Ohio State University School of Environment and Natural Resources. "As a result, the network will become fragmented, contracting into isolated, separated pools.

"If water is flowing throughout the network, fish are able to access all parts of it and make use of whatever resources are there. But when systems dry down, temporary fragmented systems develop that force fish into smaller, sometimes isolated channel reaches or pools until dry channels wet up again."

This study covers climate change's effects on surface water availability from precipitation and temperature changes. It does not take into account any withdrawals of groundwater that will be needed during droughts to support the estimated 50 percent or more increase in Arizona's population by 2050.

"These estimates are conservative," said Jaeger, who conducted the study with co-authors Julian Olden and Noel Pelland of the University of Washington. The study is published in the Proceedings of the National Academy of Sciences.

The researchers used a rainfall runoff model, the Soil and Water Assessment Tool (SWAT), which incorporates the study basin's elevation, terrain, soil, land use, vegetation coverage, and both current and future climate data, including precipitation and temperature.

"It's a hydrological model that routes water received from precipitation through the landscape, a portion of which eventually becomes streamflow in the river," Jaeger said. "We partitioned the watershed into many smaller pieces all linked to each other, with nodes placed 2 kilometers apart throughout the entire river network to evaluate if that portion of the river channel at an individual node supported streamflow for a given day."

Jaeger describes the river network, as envisioned by this model, as a mosaic of wet and dry patches. Piecing data from all of those nodes together, the researchers established an index of connectivity for the entire watershed, which predicts that the mid-century and late-century climate will reduce connectivity by 6 to 9 percent over the course of a year and by up to 12 to 18 percent during spring spawning months.

"The index decreases that are predicted by the model will affect spawning the most," said Jaeger, who also holds an appointment with the Ohio Agricultural Research and Development Center. "During the spring spawning period, fish are more mobile, traveling longer distances to access necessary habitat. Projected decreased connectivity compromises access to different parts of the network."

Flowing portions of the system will diminish between 8 and 20 percent in spring and early summer, producing lengthier channels that will dry more frequently and over longer periods of time. These changes will reduce available habitat for fish and force them to travel longer distances for resources once channels rewet, Jaeger said.

The fish are already subject to stressors on the system, including both surface and groundwater extraction for irrigation and drinking water, loss of habitat and the introduction of nonnative species that prey on the native fish, Jaeger noted. The overall system's connectivity is also already compromised, as well, because of existing dry conditions in the American Southwest.

"These fish are important cogs in the wheel of this greater ecosystem," Jaeger said. "Loss of endemic species is a big deal in and of itself, and native species evaluated in this study are particularly evolved to this watershed. In this river network that currently supports a relatively high level of biodiversity, the suite of endemic fish species are filling different niches in the ecosystem, which allows the system to be more resilient to disturbances such as drought.

"If species are pushed over the edge to extinction, then what they bring to the ecosystem will be lost and potentially very difficult to replace."

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Whats' more disgraceful is that every time you eat, resources are completely wasted. Perfectly good food that could feed a decent human being or even a dog is being wasted on the likes of you.

Shameful.

-- rockturdOh look, mummy let her little turd out of the basement to play. I hope all that global warming don't make him too dry.. oh wait..too late..he's a rockturd.This is the same turd that boasts about eating meat, one of the biggest contributors to GHGs, and yet he has the audacity to call others shameful. Well, what else would one expect from a turd.

Currently, the area has an semi-arid "steppe" climate, and only receives 12" of rain a year. Between that and an increasing human consumption of water (as populations grow), there isn't a lot of latitude for these kinds of waterways. In rainfall patterns adjust, they'll have to explore some creative means to maintain the basin's ecosystem.

Whats' more disgraceful is that every time you eat, resources are completely wasted. Perfectly good food that could feed a decent human being or even a dog is being wasted on the likes of you.

Shameful.

-- rockturdOh look, mummy let her little turd out of the basement to play. I hope all that global warming don't make him too dry.. oh wait..too late..he's a rockturd.This is the same turd that boasts about eating meat, one of the biggest contributors to GHGs, and yet he has the audacity to call others shameful. Well, what else would one expect from a turd.

Still obsessed with shit I see. Poor you. All alone in the septic tank with your waterproof computer.

This is the same turd that boasts about eating meat, one of the biggest contributors to GHGs,

Eating meat does not contribute to greenhouse gases. The carbon is cow farts comes from grass and other plants which is a natural part of the carbon cycle the same way burning firewood does not increase greenhouse gases it simply cycles them. It does not come from petroleum. The cow eats the plant, releases waste (your favorite part), the waste cycles thru the atmosphere and is taken up again by plants. No net gain. Of course you're far too stupid to understand that.

But given that you are a type of fungus you don't really get to choose what you eat do you?

https://en.wikipe...d_StatesWith the exception of a few intelligent scientific papers to the contrary we have as a global society embraced the wind turbine 'solution' whole heartedly. There are caveats in any process , this is no exception. No doubt everyone does their own research, an algorithm to encompass our ant like 24/7 behavior for the past several hundred years mixed with the planet, solar system, galaxy, universe as a whole is obviously untenable. Apparently with this verbiage I have said nothing, not unlike a computable lack of understanding of what exactly causes global warming. The dynamic is not a simple or complex platform that numbers can accommodate. Like medicine its a 'practice' not a practicum. It follows that we do not have enough time related data to render a valid opinion in the global warming debate but we should realize our activities do not have valid inferences....and so on....in the end enlist the beaver they know...